Expert: Richard Taylor, AIA - 12/5/2008

Question
I would like to add insualtion to the attic of a 1930's colonial in Milwaukee Wisconsin.  The bathroom ceiling has four light fixtures that allow warm air and moisture to pass into the cold attic area.  What is the best way to insulate the attic area around these exposed light fixtures?

Answer
Tim - thanks for your question!

Careful here - this is a life-safety issue you need to pay close attention to.  Recessed light fixtures either ARE or ARE NOT rated for insulation...if you insulate next to a non-rated recessed fixture, you run a risk of overheating and fire.

How can you tell?  Recessed fixtures carry a notice on the side that tells whether it is rated for insulation - be sure you look for this notice, if it's not there, don't insulation around it without taking certain precautions.

With the proper rating, you can place insulation (batts or loose fill) right up next to the fixture.  You might also want to consider caulking the gaps around the fixture where it passes through the plaster ceiling to stop the air flow.

Without the proper rating, you must first isolate the fixture before you insulate.  There are a couple of ways to do this.  One is to purchase pre-made insulation "boxes" from your local insulation contractor.  They're placed over the fixture in the ceiling and keep the insulation from coming in contact with the fixture.  You can still caulk the gaps.

Another way is to isolate the fixtures yourself.  You could do this with a section of metal heating duct or any other non-flammable material.  The duct would slip over the fixture, leaving a generous space between the fixture and the walls of the duct, and the insulation placed around it.

Be sure the section of duct is as long as the insulation is deep.  And with this "homemade" solution, don't cover the top - leave it open to allow the fixture to disapate heat.  And of course caulk the gaps.

Loose-fill insulation is better than batts for this application; many home-improvement stores sell "blown-in" cellulose insulation by the bag and will rent you the machine to blow it in.

Good luck with your project!

Hope this helps,

Richard Taylor, AIA
www.rtastudio.com
www.rtaplans.com